Good things come to those who wait. Actually I missed the email indicating someone actually responded to my crazy post.
Ok, to the best of my aged memory, she was looking for texture and visual indicators. I remember the look of mold on some of the slices, and her reaction as any young female teen would. Priceless!
Results? Homemade bread spoiled the fastest when looking at the mold that appeared in just a day or so (no preservatives). Then the other "healthy" breads started to fail growing very unusual and pretty molds. But the winner of the bread that lasted the longest was the cheapest white bread she could find. It never got moldy, just hard as a rock. The packaging indicated it contained additives to retard spoilage that are probably banned as carcinogenic by now!!!
She got a 1st place on that science project and it stuck with her. Today she has her doctorate in pharmacy and manages a retail pharmacy.